After checking him out, the vet could only tell us it was idiopathic vestibular disease. She explained that idiopathic just means they can't tell what the cause is. Because the the condition made Sunny so dizzy, the vet said he wouldn't be able to lower his head to eat or drink. She gave him an antibiotic injection and sent us home with an IV bag of saline solution to inject into his scruff to keep him hydrated.
He began having discharge from the ear on the "down-side" so the vet prescribed some expensive ear drops. Happily, he's improved to the point where his head is only slightly cocked and he can walk around pretty good. But if he moves suddenly, he easily becomes disoriented and falls over. After eighteen days of treatment, he's still not back to normal. We will take him back to the vet on Wednesday for a follow-up.
I blame it all on the upcoming property tax refund that comes in August. Once again proving Sparrow's Law: Your expenses will always increase to equal your income.